Multi-pivot thrombectomy device

ABSTRACT

A device may be used for capturing and retrieving vascular debris. The device may comprise: at least two segments radially expandable from a collapsed state to an expanded state, each of the at least two segments having (a) a waist comprising a radially largest region of the segment and (b) two longitudinal ends; at least one intermediate portion, each of the at least one intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter less than a diameter of the waist; a tether attached to a proximalmost of the at least two segments and configured to position the at least two segments; wherein each of the at least two segments comprises at least two struts that extend longitudinally from a proximal end to a distal end of the segment, the at least two struts tapering from the waist radially inward toward a longitudinal axis of the device as the at least two struts approach an adjacent intermediate portion.

BACKGROUND

The presence of an vascular debris (e.g., thrombus, embolus) in a vasculature can cause a number of significant health problems. A thrombus is a stationary blood clot that is often found along the wall of a blood vessel and may cause vascular obstruction. Thrombus is usually formed in vivo as the final product of the blood coagulation step in hemostasis. In relatively large blood vessels, a thrombus will typically decrease the blood flow through that vessel. In smaller blood vessels, blood flow may be completely cut-off resulting in death of tissue supplied to that vessel. A dislodged thrombus is often referred to as an “embolus.” Vascular obstruction or ischemia is the insufficient supply of blood to an organ, usually due to a blocked blood vessel. Symptoms of vascular obstruction may include chest pains, loss of vision, and in some cases death. Thrombectomy is a surgical procedure that involves the removal of a thrombus from a patient's vasculature.

SUMMARY

Certain vascular devices are important for their intervening roles in patients with vascular debris in their vasculature. Some techniques for removing vascular debris utilize balloon catheters, aspiration catheters, and the like. These techniques may have safety (e.g., intimal lesions) and performance issues (e.g., use limited to certain arteries). Therefore, there is a need to provide additional systems and methods for removing vascular debris from a vasculature that are safe and overcome some of the existing performance issues.

Although at least one embodiment is described herein with respect to thrombus and thrombectomy, the subject technology may be used to remove any vascular debris that is compatible with one or more embodiments with the subject technology.

The subject technology is illustrated, for example, according to various aspects described below. Various examples of aspects of the subject technology are described as embodiments. These are provided as examples and do not limit the subject technology. It is noted that these embodiments may be combined in any combination.

Some embodiments provide a system for retrieving vascular debris in a vasculature comprising at least two segments radially expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; at least one intermediate portion, each intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter comprising the radially largest region of the pivot; an outer lumen that is configured to at least partially encapsulate the segments in the compressed state; and a tether that is configured to retrieve a segment in the expanded state into the outer lumen.

In some embodiments, at least one segment is substantially spherical. In some embodiments, the segments comprises radially-expandable struts. In some embodiments, a segment comprises at least two struts. In some embodiments, a segment comprises at least three struts. In some embodiments, a segment comprises at least four struts. In some embodiments, a segment comprises at least five struts. In some embodiments, a segment comprises at least six struts. In some embodiments, a segment comprises at least seven struts. In some embodiments, a segment comprises at least eight struts. In some embodiments, a segment comprises at least nine struts. In some embodiments, a segment comprises at least ten struts. In some embodiments, a segment comprises at least eleven struts. In some embodiments, a segment comprises at least twelve struts. In some embodiments, at least one strut diverges from the longitudinal axis, divides into at least two struts, merges with an adjacent strut, and converges toward the longitudinal axis.

Some embodiments provide a system comprising at least three segments. Some embodiments provide a system comprising at least four segments. Some embodiments provide a system comprising at least five segments. Some embodiments provide a system comprising at least six segments. Some embodiments provide a system comprising at least seven segments. Some embodiments provide a system comprising at least eight segments. Some embodiments provide a system comprising at least nine segments. Some embodiments provide a system comprising at least ten segments.

Some embodiments provide a system for retrieving vascular debris in a vasculature comprising at least three segments expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; at least two intermediate portion, each intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter comprising the radially largest region of the pivot; an outer lumen that is configured to encase the segments in a compressed state; and a tether that is configured to retract the segments into the outer lumen.

Some embodiments provide a method of retrieving vascular debris from a vasculature comprising inserting into the vasculature of a patient at least a portion of an outer lumen comprising a distal opening and encasing at least two or more segments expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; releasing at least a portion of a segment outside the distal opening wherein at least a portion of the segment expands to engage the vascular debris; and retrieving the segment and at least a portion of the vascular debris inside the outer lumen.

In some embodiments, the vascular debris is a thrombus or an embolus. In some embodiments, the outer diameter of the outer lumen is no larger than 50% of the diameter of the vasculature.

Additional features and advantages of the subject technology will be set forth in the description below, and in part will be apparent from the description, or may be learned by practice of the subject technology. The advantages of the subject technology will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide farther explanation of the subject technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide further understanding of the subject technology and are incorporated in and constitute a part of this specification, illustrate aspects of the subject technology and together with the description serve to explain the principles of the subject technology.

FIG. 1 illustrates embodiments of a vascular intervention device.

FIG. 2 illustrates a partial end view of the device of FIG. 1, taken along the direction indicated by the arrows 2-2 in FIG. 1.

FIG. 3 illustrates a partial end view of the device of FIG. 1, taken along the direction indicated by the arrows 3-3 in FIG. 1

FIG. 4 illustrates an example configuration of a widened portion for use on struts of device of FIG. 1.

FIG. 5 illustrates a cut pattern for use in making embodiments of the device.

FIG. 6 illustrates a detail view of a proximal section of the cut pattern of FIG. 5.

FIG. 7 illustrates a detail view of a distal section of the cut pattern of FIG. 5.

FIG. 8 illustrates a device made with the cut pattern of FIGS. 5, 6, and 7.

FIG. 9 illustrates a detail view of the proximal section of the device of FIG. 8.

FIG. 10 illustrates a proximal end view of the proximal section of the device of FIG. 8.

FIG. 11 illustrates a detail view of the distal section of the device of FIG. 8.

FIG. 12 illustrates a distal end view of the distal section of the device of FIG. 8.

FIGS. 13A and 13B illustrate embodiments of a vascular intervention device.

FIGS. 14A, 14B, and 14C illustrate embodiments of a vascular intervention device delivery system in a vasculature.

FIGS. 15A, 15B, and 15C illustrate embodiments of a vascular intervention device delivery system in a vasculature.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth to provide a full understanding of the subject technology. It will be apparent, however, to one ordinarily skilled in the art that the subject technology may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the subject technology.

While some of the embodiments described herein specifically relate to a vascular intervention device having two segments, the described features may generally be extended to devices having two or more segments.

Vascular Intervention Device

FIGS. 1-3 illustrate an example embodiment of a vascular intervention device 50 that may be used to remove vascular debris (e.g., thrombus) that can obstruct the normal flow of blood in a vasculature. As illustrated in FIG. 1, the device 50 comprises two segments (a proximal segment 52 and a distal segment 56) and a pivot section 54. Referring to FIGS. 14A-15C, the device 50 can be delivered via a sheath such as a catheter 144 into the vasculature and positioned at or near a target site in order to expand, engage and retrieve vascular debris (thrombus 142). It will be appreciated that the device 50 may be more compliant than the vasculature in which it is deployed such that it may be somewhat misshapen after being deployed, and that certain shapes described herein are when the device 50 is an expanded (e.g., further expanded) state with no restriction.

While one or more embodiments described herein relate to a vascular intervention device having two segments, the device 50 may comprise any number of segments that is compatible with one or more embodiments of the subject technology. The total number of segments (one proximal, one distal, and any number of intermediate segments starting from zero) may range from about 2 to about 15 or more depending on the a number of factors such as, but not limited to, size, shape, and location of the vascular debris within a vasculature. It is generally desirable that the device 50 is at least as long as the targeted vascular debris.

FIGS. 13A-15C illustrate other embodiments of the vascular intervention device 50 that include three or more segments. As shown in FIGS. 13A and 14A-14C, the vascular intervention device 50 may have three segments, namely a proximal segment 52, a distal segment 56, and an intermediate segment 134 a. FIGS. 13B and 15A-15C illustrate a vascular intervention device 50 having four segments, namely a proximal segment 52, a distal segment 56, and two intermediate segments 134 a and 134 b.

A vascular intervention device having a plurality of segments may provide a number of advantages related to the removal of vascular debris in a vasculature. For example, certain segments (e.g., distal, intermediate) may include widened portions 78 (FIGS. 1 and 4) that may be positioned distal to the vascular debris and filter emboli that may be generated during the use of the device 50. Moreover, a plurality of segments may also provide a greater margin for error when positioning and deploying the vascular intervention device 50 near a target site.

Proximal Segment

Referring to the embodiment illustrated in FIGS. 1 and 13A-13B, the proximal segment 52 can be radially self-expanding and may comprise a plurality of radially self-expanding struts 58. Six struts 58 are depicted in the proximal segment 52 of FIGS. 1-2 (and only four of the struts 58 are visible in FIG. 1), but more or fewer struts may be employed in the proximal segment 52, as described in further detail herein. For example, the proximal segment of FIG. 13A includes 8 struts (only five of which are visible). The struts 58 converge toward the radial center of the proximal segment 52 at the distal end of the proximal segment 52, where the proximal segment 52 joins the proximal end of the pivot section 54, and at the proximal end of the proximal segment 52, where the proximal segment 52 joins a proximal end portion 60 of the device 50.

The proximal end portion 60, located at the proximal end of the device 50, may comprise an interconnection of the proximal ends of the struts 58, which in turn can be coupled to a tether 140 (FIGS. 14A-15C) or other suitable means that facilitate deployability and/or re-sheathability and re-positionability of the device 50. Such a tether 140 may be configured to connect the device 50 to a delivery member such as a pusher wire (not shown).

When the device 50 is in a fully-expanded configuration shown in FIGS. 1-3 and 13A-13B, the proximal struts 58 extend radially outward as they advance from the proximal and distal ends of the proximal segment 52, thereby forming proximal and distal tapering portions or faces 62, 64 of the proximal segment. The struts 58 reach their radially outermost extent in a waist portion 66 of the proximal segment 52, between the proximal and distal faces 62, 64. It will be appreciated that the distal and intermediate segments may have analogous features. In the depicted waist portion 66, the struts 58 are curved and form curving radial crests or peaks. Alternatively, in the waist 66 the struts 58 can be flat and generally straight and parallel, to form an elongate and/or cylindrical waist 66.

In one or more embodiments, the struts 58 of the proximal segment 52 can have a substantially rectangular or flat cross section (e.g., where the struts 58 comprise uncut portions of a metallic tube or sheet). The struts 58 can alternatively have a substantially round (e.g., circular, elliptical, ovoid) cross section (e.g., where the struts 58 comprise round filaments). The proximal segment 52 can comprise two or more struts 58, or between two and twelve struts 58. Although the proximal segment 52 depicted in FIGS. 1-3 comprises six struts 58, the proximal segment can alternatively comprise two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve struts 58. Still other numbers of struts are possible. As seen in FIG. 2, the proximal struts 58 may be equally angularly spaced and/or oriented around the central longitudinal axis of the device 50 (e.g., six struts 60° apart from each adjacent strut as shown in FIG. 2, two struts 180° apart from each other, three struts 120° apart, four struts 90° apart, etc.). Although the arrangement of the struts are shown in the figures as substantially isometric, the arrangement can place the struts in various angles relative to each other (e.g., six struts varying about 20°, about 40°, about 50°, about 70°, and about 80° apart from each adjacent strut).

Each of the segment may be reversibly expandable from a collapsed state to an expanded state, which allows portions of the device 50 to expand after deployment and also enables the device 50 to be retrieved after deployment (FIGS. 14C and 15C). Referring to FIGS. 1 and 13A-13B, the tapered proximal face 62 of the proximal segment 52 may allow the device 50 or portions thereof (e.g., the proximal segment 52) to be retrieved back (e.g., in the proximal direction) into a delivery catheter via a distal opening thereof. For example, if the device 50 is being pulled into a catheter, the tapered proximal face 62 may radially compress the proximal segment 52. The ability to retrieve the device 50 or proximal segment 52 facilitates removal or re-positioning of the device 50 if an initial placement is not satisfactory. It will be appreciated that the distal and/or intermediate segments have similar features that also enable or facilitate the retrieval of the device into a delivery catheter via a distal opening thereof.

Distal Segment

The distal segment 56 can be radially self-expanding and comprise a plurality of radially self-expanding struts 68. Eight struts 68 are depicted in the distal section 56 of FIGS. 1, 3, and 13A-13B (and only five of the struts 68 are visible in FIG. 1), but more or fewer struts may be employed in the distal segment 56, as will be described in further detail below. The struts 68 converge toward the radial center of the distal segment 56 at the proximal end of the distal segment 56, where the distal segment 56 joins the distal end of the pivot section 54, and at the distal end of the distal segment 56, where the distal segment 56 joins a distal end portion 70 of the device 50.

When the device is in the fully-expanded configuration shown in FIGS. 1-3 and 13A-13B, each segment may include struts that extend radially outward as they advance from one end of the segment to the other end, thereby forming tapering portions or faces. For example, in FIGS. 1 and 13A-13B, the distal struts 68 extend radially outward as they advance from the proximal and distal ends of the distal segment 56, thereby forming proximal and distal tapering portions or faces 72, 74 of the distal segment 56. The struts 68 reach their radially outermost extent in a waist portion 76 of the distal segment 56, between the proximal and distal faces 72, 74.

When the device 50 is deployed in a patient's vasculature, any portion of the device such as the waist or tapering face of the distal, intermediate, and/or proximal segment may engage the vascular debris 142 (FIGS. 14A-15C). Referring to FIGS. 1 and 13A-13B, the waist portion 76, the struts 68 are curved and form curving radial crests or peaks. Alternatively, in the waist 76 the struts 68 can be flat and generally straight and parallel, to form an elongate and/or cylindrical waist 76.

The struts 68 of the distal segments can have a substantially rectangular or flat cross section (e.g., where the struts 68 comprise uncut portions of a metallic tube or sheet). FIGS. 1 and 13A-13B shows that struts 68 can alternatively have a substantially round (e.g., circular, elliptical, ovoid) cross section (e.g., where the struts 68 comprise round filaments). A circular, elliptical or ovoid cross-section may be imparted to otherwise square or rectangular struts 58/68 by processing steps such as electropolishing. The distal segment can comprise two or more struts 68, or between two and twelve struts 68. Although the distal segment 56 depicted in FIGS. 1-3 comprises eight struts 68, the distal segment can alternatively comprise two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve struts 68. Still other numbers of struts are possible. As seen in FIG. 3, the distal struts 68 may be equally angularly spaced and/or oriented around the central longitudinal axis of the device 50 (e.g., eight struts 45° apart from each adjacent strut, two struts 180° apart from each other, three struts 120° apart, four struts 90° apart, etc.).

Widened Portion

One or more of the struts of a segment(s) (preferably a distal and/or an intermediate segment) can optionally include or form widened portions or leaves 78 on the distal face 74 of the distal segment. As seen in FIG. 3, the widened portions 78 can provide a blocking function to prevent or reduce the passage of materials or fluids through the distal face 74. For example, in one aspect, the widened portions 78 may be wider than a width of the struts forming the proximal face of the distal segment 56. This feature enables certain segments to act as filters to capture or engage thrombi, emboli, or other structures that form or are present after deployment of the vascular intervention device 50.

FIG. 4 depicts one example of a widened portion 78 that may be employed with any of the embodiments of the device 50 disclosed herein. One, some or all of the widened portions 78 (and struts 68) of the device 50 may take the form depicted in FIG. 3 and further described herein. To form the widened portion 78, the strut 68 can be longitudinally split into sub-struts 82 that surround an opening 84 in the widened portion 78. The widened portions may also alternate or vary in size from one strut 68 to the next.

The struts 68 can be configured to form the sub-struts 82 and opening 84 via tapering portions 86 on either side of the opening 84. Distal and proximal of the tapering portions 86, the struts 68 can be of substantially uniform width. The proximal portion 88 of the strut 68 (proximal of the widened portion 78) can be wider than the distal portion 90 of the strut 68 (distal of the widened portion 78). In such a case, the width of the proximal strut portion 88 can nonetheless be substantially uniform from the proximal tapering portion 86 to the intermediate portion 54, and the width of the distal strut portion 90 can be substantially uniform (but narrower than the width of the proximal strut portion 88) from the distal tapering portion 86 to the distal tip portion 70 of the device 50. By employing struts 68 that are narrower in their distal portions 90 than in their proximal portions 88, the distal face of the distal portion 56 can be made relatively compliant and therefore more easily conformable, while retaining a desired degree of stiffness in the proximal components of the device 50.

In another aspect, the widened portions 78 may comprise a first and second ramp, where the first ramp extends from an edge of the strut to an edge of the widened portion 78, and the second ramp extends from the edge of the widened portion 78 to the edge of the strut. In this manner, the widened portions 78 can increase the occlusiveness of the distal face when desirable. Instead of or in addition to the widened portion(s) 78, a mesh, membrane or other covering may be employed on the distal face 74 to perform similar function(s).

Intermediate Segment

Referring to FIGS. 13A-13B, the device 50 may optionally include intermediate segment(s). The intermediate segment 134 a, 134 b can be radially self-expanding and comprise a plurality of radially self-expanding struts 138. Eight struts 138 are depicted in the intermediate segment 134 a, 134 b of FIGS. 13A-13B, but more or fewer struts may be employed in the intermediate segment 134 a, 134 b, as will be described in further detail below.

Referring to FIG. 13A-13B, the struts 138 converge toward the radial center of the intermediate segment 134 a at the proximal end of the intermediate segment 134 a, where the intermediate segment 134 a joins the distal end of the pivot section 54 a, and at the distal end of the intermediate segment 134 a, where the intermediate segment 134 a joins proximal end of pivot section 54 b. Referring to FIG. 13B, the struts 139 converge toward the radial center of the intermediate segment 134 b at the proximal end of the intermediate segment 134 b, where the intermediate segment 134 b joins the distal end of the pivot section 54 b, and at the distal end of the intermediate segment 134 b, where the intermediate segment 134 b joins proximal end of pivot section 54 c.

When the device is in the fully-expanded configuration shown in FIGS. 13A-13B, each segment may include struts that extend radially outward as they advance from one end of the segment to the other end, thereby forming tapering portions or faces. For example, in FIGS. 13A-13B, the intermediate struts 138 extend radially outward as they advance from the proximal and distal ends of the intermediate segment 134 a, 134 b, thereby forming proximal and distal tapering portions or faces 172, 174 of the intermediate segment 134 a, 134 b. The struts 138 reach their radially outermost extent in a waist portion 136 of the intermediate segment 134 a, 134 b, between the proximal and distal faces 172, 174.

Referring to FIGS. 13A-13B, the struts 138, 139 of the intermediate segment 134 a, 134 b can have a substantially rectangular or flat cross section (e.g., where the struts 138, 139 comprise uncut portions of a metallic tube or sheet). FIGS. 13A-13B show that struts 138, 139 can alternatively have a substantially round (e.g., circular, elliptical, ovoid) cross section (e.g., where the struts 68 comprise round filaments). A circular, elliptical or ovoid cross-section may be imparted to otherwise square or rectangular struts 58/68 by processing steps such as electropolishing. The intermediate segment 134 a, 134 b can comprise two or more struts 138, 139, or between two and twelve struts 138, 139.

In some embodiments, one or more segments (proximal, distal, and intermediate) may be substantially similar in shape. In the embodiment shown in FIGS. 13A-13B, the proximal, distal, and intermediate segments have the same number of struts. In other embodiments, the segments may comprise different number of struts. In some embodiments, a segment may have the same number of struts as at least one other segment.

Pivot Section and Pivotability

Referring to FIG. 1, the pivot section 54 connects adjacent segments (e.g., 52 and 5 in FIG. 1), and can be relatively short and relatively narrow (relative to the length and width of the proximal and distal segment 52, 56 when they are expanded). In some embodiments, the device may include one or more pivot sections that depend on the number of segments (proximal, distal, and intermediate). In the embodiment shown in FIG. 13A, the device includes two pivot sections 54 a, 54 b that are similar in structure to the pivot section 54 shown in FIG. 1.

So configured, the pivot section (e.g., 54, 54 a, 54 b, 54 c) allows a relatively distal segment to pivot with respect to a relatively proximal segment and thereby allow the device 50 to be deployed in tortuous vasculature. For example, referring to FIG. 1, the distal segment 56 can pivot with respect to proximal segment 52. In FIG. 13A, the distal segment 56 can pivot with respect to intermediate segment 134 a and the intermediate segment 134 a can pivot with respect to distal segment 56.

Referring to FIG. 1, the pivot section 54 may permit “multiaxial” pivoting or tilting, e.g. at least about a first axis through the pivot section 54 and orthogonal to the plane of the page in FIG. 1, and about a second axis through the pivot section 54 and orthogonal to the first axis. The pivot section 54 may permit “omniaxial” pivoting or tilting, about the first and second axes described above, and any radially-oriented axis passing through the pivot section 54.

The device may provide multiaxial or omniaxial pivoting or tilting up to relatively high deflection angles (e.g., up to 90 degrees) without significantly affecting the ability of the segments to maintain their expanded states and engage the vascular debris 142 (FIGS. 14A-15C). This capability can be facilitated by making the proximal struts 58 independent of the adjacent struts (e.g., distal struts 68) as depicted in FIG. 1. The two groups of struts are independent of each other in that forces acting solely on, and/or deflections occurring solely in, the proximal struts 58 do not significantly affect the ability of the distal struts 68 to maintain their expanded state, and forces acting solely on, and/or deflections occurring solely in, the distal struts 68 do not significantly affect the ability of the proximal struts 58 to maintain their expanded state.

While some of the embodiments described herein specifically relate to a vascular intervention device having two segments, the described features may generally be extended to devices having two or more segments.

Referring again to FIG. 1, one, some or all of the struts 58 can bend or pivot with respect to the pivot section 54 independently of one, some or all of the struts 68 and vice versa. The pivot section 54 may promote independence by interconnecting the struts 58 and the struts 68 in a radially central region of the device 50, and physically and functionally separating them, absorbing bending stresses from the struts 58 and the struts 68 rather than transmitting them from the struts 58 to the struts 68 or vice versa.

Instead of, or in addition to, independence of the proximal struts 58 as a group, from the distal struts 68 as a group, the struts 58 may be independent of each other (within the group of struts 58), and/or the struts 68 may be independent of each other (within the group of struts 68). In the device 50 as depicted in FIGS. 1-3, the proximal struts 58 are independent of each other and the distal struts 68 are independent of each other. Each proximal strut 58 can bend or pivot with respect to the pivot section 54 independently of the other proximal struts 58, and each distal strut 68 can bend or pivot with respect to the pivot section 54 independently of the other distal struts 68. Independence is promoted within each group of struts 58, 68 by interconnecting them only at their proximal and distal ends, and in a radially central region of the device 50.

It should be noted, however, that independence as used herein does not exclude interconnecting independent components by members (e.g. membranes, very fine wires and the like) that are insufficiently rigid to cause one component to significantly affect the action of the other. The proximal struts 58 and/or the distal struts 68 can also be independent of each other, but only within a limited region of the segment(s). For example, the proximal struts 58 may be independent of each other within the distal face 64 of the proximal segment, and/or the distal struts 68 may be independent of each other within the proximal face 72 of the distal segment 56.

The tapered distal face 64 of the proximal segment 52 and tapered proximal face 72 of the distal segment 56 also allow the sections 52, 56 to pivot significantly without contact between the segments 52, 56 other than at the pivot section 54.

The pivot section can be rigid or flexible. Where the pivot section is rigid, the pivotability of the device 50 can be provided by the flexibility and/or independence of the struts 58 in the distal face 64 of the proximal segment 52 and of the struts 68 in the proximal face 72 of the distal segment 56. In this example, the proximal and distal segments are able to pivot multiaxially relative to each other without requiring plastic deformation of the pivot section. Each of struts 58 and struts 68 may be capable of flexing, extending, bowing, straightening, bending, or other elastic or plastic deformation along the length or a portion thereof.

Referring to FIGS. 1 and 13A-13B, as struts independently flex and extend, segments 52, 56, 134 a, 134 b can pivot about pivot section and relative to each other. For example, struts on one side of a section may flex (e.g., bend), and struts on an opposing side of a segment may extend (e.g., straighten), whereby the segment pivots about the region where the struts connect to pivot section.

According to embodiments, such action is facilitated along one or more segments and/or sections of the device. According to embodiments, this pivot action is provided without requiring plastic deformation of pivot section or any action along the length of pivot section. The pivot section can comprise a short length of hypotube (e.g., a short length of uncut hypotube) which may be flexible or rigid. According to embodiments, the pivot section can comprise a flexible coil, longitudinally oriented such that its winds spiral around the central longitudinal axis of the device 50, or the pivot section can comprise a ball-and-socket joint, a length of flexible wire, or other flexible member.

Materials

The device 50 can further comprise one or more radiopaque markers (e.g. coils) coupled to or wound around portions of the device. For example, the device 50 can include radiopaque markers on one, two or all three of the proximal end portion 60, pivot section 54, and distal end portion 70. Instead of or in addition to those markers, the device 50 can include radiopaque markers on one or more of the struts 58, and/or on one or more of the struts 68. According to embodiments, when any of the proximal end portion 60, intermediate segment 54, or distal end portion 70 defines a central lumen therethrough (e.g., when the device 50 is cut or etched from a tube or sheet), radiopaque material may be placed within some, one or all of those lumens to make the proximal end portion 60, pivot section 54, and distal end portion 70 radiopaque. For example, radiopaque material maybe provided within a lumen of at least one of the proximal end portion 60, pivot section 54, and distal end portion 70 with securement at one or both of the ends of the lumen.

The device can comprise a self-expanding, super elastic, and/or a shape-memory material (e.g., comprising Nitinol, CoCr alloy, shape memory polymers (e.g., polyglycolic acid, polylactic acid), etc.), thereby causing the device to be self-expanding under certain conditions (e.g., when not restrained by a catheter). In some embodiments, the proximal segment, the pivot section, the distal segment, and/or intermediate segment(s) may comprise different materials. For example, the distal segment 56 may comprise polymer material while the proximal segment and the pivot section comprise metallic material, a different polymer material, etc. For another example, the distal segment may comprise metallic material while the proximal segment and the pivot section comprise different metallic materials, polymer material, etc. Other combinations of materials are also possible. The device can assume a low profile compressed state (e.g., confined within a catheter) for delivery. When cut from a tube or sheet, the device may assume substantially the diameter of the tube or rolled sheet when in the compressed state. Upon deployment from the catheter, the device expands from the compressed state to an expanded state.

The various versions of the vascular intervention device 50 disclosed herein can be manufactured in a process comprising cutting (or electrochemically etching) and shaping a metallic tube or sheet (e.g., a laser cut hypotube or sheet). A laser or electrochemical etcher may cut out portions of the tube, leaving in place the various structural elements of the proximal segment, the pivot section(s), the intermediate segment(s), and/or the distal segment. In the device 50 depicted in FIGS. 1-3 and 12, or the device 50 depicted in FIG. 4, the proximal segment 52, the pivot section 54, and the distal segment 56 can be integrally formed from a metallic tube and not cut away from each other. In devices 50 in which all segments and sections 52, 54, 56 are integrally fabricated by being cut, etched, etc. from the same tube or sheet, the device 50 is of single-piece construction, taking the form of a single, partial tube or sheet. Alternatively, the sections 52, 54, 56 can be formed separately and then assembled together using any suitable technique, such as welding, gluing, interlocking, crimping, swaging, braiding, deposition, etc. Where the pivot section 54 comprises a coil, the segments 52 and 56 may be formed from the same or separate tubes, and then attached to either end of the coil using any such suitable technique.

After cutting from one or more tubes, the device 50 or segments/section(s) 52/54/56 thereof may be reshaped and heat treated to impart shape setting to the device or segments/section(s). The shape setting process may include several steps comprising, for example, stretching and confining the cut tube into a new shape during the heat treatment. At the end of each heat treatment step, the cut tube assumes the shape in which it was confined during the heat treatment process. The final shape (e.g., expanded state) and size may obtained by several such steps. The device 50 or cut tube may be electropolished during manufacture, which can reduce the initial wall thickness of the tube to a final, desired thickness.

FIGS. 5-12 depict a version of the device 50 (and a cut pattern 300 for constructing it) that can be similar to any of the other versions or embodiments of the device 50 disclosed or summarized herein, in structure, configuration, function, method of manufacture, method of use, and material choice, except as further discussed herein. In the device 50 of FIGS. 5-12, the struts 58 of the proximal section 52 comprise a number (e.g. 6, as depicted, or any other suitable number) of proximal strut portions 58 a and a corresponding number of distal strut portions 58 b.

The proximal portions 58 a and the distal portions 58 b are rotated or shifted laterally with respect to each other, such that each proximal portion 58 a opposes (e.g., approximately one-half of each of) two distal portions 58 b, and vice versa. From the distal end of each proximal portion 58 a, two sub-struts 58 c extend distally to the two distal portions 58 b that oppose (or are longitudinally adjacent) the proximal portion 58 a from which the sub-struts 58 c extend. Accordingly, each proximal portion 58 a is connected to the two adjacent or opposing distal portions 58 b (and vice versa) via sub-struts 58 c. For example, each strut may have a proximal end, a distal end, and a center portion therebetween, the center portion connected to adjacent struts.

In another example, each strut may extend from an origination junction and be divided into a first and second branch, wherein the first branch is connected to a first adjacent strut and the second branch is connected to a second adjacent strut. In this example, a length of the first branch and a length of the second branch may be different such that a connecting point between the strut and the first adjacent strut is disposed at a different longitudinal position than a connecting point between the strut and the second adjacent strut.

According to embodiments, the length of the first branch and the length of the second branch may be the same. In another example, at least one strut may extend proximally from the inter mediate section and be divided into a first and second branch at or near the waist of the proximal section. The first branch may be connected to the first adjacent strut and the second branch may be connected to the second adjacent strut. The first and second adjacent struts may extend proximally from the waist of the proximal section toward the radially central region of the device.

According to embodiments, one or more sections 52, 56 may have a first plurality of struts extending from a proximal end of the section and a second plurality of struts extending from the distal end of the section. The first and second plurality of struts may be interconnected at the waist or middle portion of the section by a third plurality of struts. Each of the first plurality of struts may be connected to two or more of the third plurality of struts. Each of the second plurality of struts may be connected to two or more of the third plurality of struts. The number of the first plurality of struts may equal the number of the second plurality of struts. The number of the third plurality of struts may be double, triple, or another multiple of one or each of the number of the first plurality of struts and the number of the second plurality of struts.

When the proximal section 52 of the device 50 is expanded, the sub-struts 58 c extend both longitudinally to interconnect the proximal end portion 60 and the intermediate section 54, and laterally or circumferentially to each neighboring proximal or distal portion 58 a or 58 b. The resulting lateral or circumferential interconnection of the struts 58 of the proximal section 52 increases the outward radial force exerted by the proximal section 52 (and the inward radial force that the proximal section 52 can withstand without collapse) when expanded. In addition, the lateral/circumferential interconnection of the struts of the proximal section 52 reduces the tendency of the expanded struts 58 to bunch together in the vessel or “half-moon.” Further, the lateral/circumferential interconnection of the struts of the proximal section maintains the three dimensional shape of the proximal section. Moreover, the lateral/circumferential interconnection of the struts of the proximal section provides structural support for the interconnected struts

As depicted in FIGS. 5-6 and 8-9, the sub-struts 58 c (e.g., the peaks thereof) can form the waist 66 of the proximal segment 52, or otherwise comprise the radially outermost portion of the proximal segment 52. The sub-struts 58 c can optionally be approximately longitudinally centered on the longitudinal midpoint of the proximal segment 52, such that the midpoint approximately evenly divides the sub-struts 58 c in the longitudinal direction. Such an arrangement is also depicted in FIGS. 5-6 and 8-9.

As depicted in FIGS. 7 and 11-12, the widened portions 78 on the distal tapering portion 74 of the distal segment 56 can be formed via the lateral/circumferential interconnection arrangement employed in the proximal segment 52 and discussed above. To accomplish this, the proximal strut portions 88 and distal strut portions 90 of the distal struts 68 are rotated or shifted laterally with respect to each other, such that each proximal portion 88 opposes (e.g., approximately one-half of each of) two distal portions 90, and vice versa. From the distal end of each proximal portion 88, two sub-struts 82 extend distally to the two distal portions 88 that oppose (or are longitudinally adjacent) the proximal portion 88 from which the sub-struts 82 extend. Accordingly, each proximal portion 88 is connected to the two adjacent or opposing distal portions 90 (and vice versa) via sub-struts 82. For example, at least one strut may extend distally from the intermediate section and be divided into a first and second branch at or near the waist of the distal section. The first branch may be connected to the first adjacent strut and the second branch may be connected to the second adjacent strut. The first and second adjacent struts may extend distally from the waist of the distal section toward the radially central region of the device.

When the distal segment 56 of the device 50 of FIGS. 5-12 is expanded, the sub-struts 82 extend both longitudinally to interconnect the pivot section 54 and the distal end portion 70, and laterally or circumferentially to each neighboring proximal or distal strut portion 88 or 90. In addition, the lateral/circumferential interconnection of the struts 68 of the distal segment 56 reduces the tendency of the expanded struts 68 to bunch together once deployed in the vessel or “half-moon.” Further, the lateral/circumferential interconnection of the struts of the distal segment maintains the three dimensional shape of the distal section. Moreover, the lateral/circumferential interconnection of the struts of the distal segment provides structural support for the interconnected struts.

As depicted in FIGS. 5, 7 and 11-12, the widened portions 78 and the sub-struts 82 can be located on the distal face 74 of the distal portion 56. The widened portions 78 and sub-struts 82 can optionally be located wholly distal of the waist 76 of the distal portion 56. Such an arrangement is also depicted in FIGS. 5-6 and 8-9. In other aspects, the widened portions may resemble the structures as disclosed elsewhere herein.

Dimensions

Although the device 50 is depicted in its expanded state in FIGS. 1-3, the device 50 can have a contracted state (“collapsed state”) in which the proximal and distal segments 52, 56 take on a smaller diameter than in the expanded state. For example, in the contracted state the segments 52, 56 can have a diameter small enough to fit within a delivery device, such as a microcatheter. Where the segments and sections 52, 54, 56 are cut from a single tube, the diameter of one or both of the proximal and distal segments 52, 56 when in the contracted state can be substantially equal to the diameter of the tube from which the device 50 is cut, and/or substantially equal to the diameter of the pivot section 54.

The device may be of any dimension that is compatible with one or more embodiments of the subject technology. In some embodiments, the diameter of the waist (e.g., 66, 76) when expanded may be from about 2 mm to about 20 mm. In some embodiments, the diameter of the waist when contracted may be from about 0.25 mm to about 0.75 mm. In some embodiments, the length of the a segment when expanded may be from about 2 mm to about 20 mm. In some embodiments, the width of a strut may be from about 0.075 mm to about 0.15 mm. In some embodiments, the thickness of a strut may be from about 0.025 mm to about 0.10 mm. In some embodiments, the length of the pivot section may be from about 0.01 mm to about 5 mm. In some embodiments, the diameter of the pivot section may be from about 0.25 mm to about 0.75 mm. In some embodiments, the wall thickness of the pivot section may be from about 0.025 mm to about 0.10 mm.

Thrombectomy Embodiments

In the embodiment shown in FIGS. 14A-14C, the vascular intervention device 50 is at least partially encapsulated by a sheath (e.g., catheter 144) which has been inserted into a vasculature 146. As shown in FIG. 14A, the vascular intervention device 50 is in a collapsed state and the catheter 144 is positioned at or near vascular debris 142 which resides within a vasculature 146. FIG. 14A represents one possible configuration of vascular intervention device 50 prior to its deployment from the catheter 144. As shown in FIGS. 14A-14B and 15A-15B, the thrombus 142 is adhered to an inner wall of the vasculature 146.

FIG. 14B shows a vascular intervention device 50 in a deployed or partially-deployed state. As shown in FIG. 14B, the distal segment 56 has been moved distally outside of the distal opening 150 of the catheter 144 and is now in an expanded state. A distal or proximal motion of the vascular intervention device 50 is generally initiated by a user who can controllably operate the device 50 at the proximal end (not shown) and may be accomplished by any number of means, for example, proximal motion of the catheter 144, distal motion of the device 50, or both. A user may operate an actuator which is coupled to a tether 140 which in turn is coupled to the device 50 as shown in FIGS. 14A-14C. As shown in FIG. 14B, the distal segment 56 can expand to the expanded state and engage a thrombus 142. In the particular embodiment shown in FIG. 14B, a portion of the vascular intervention device 50 is still encapsulated by the sheath. In other embodiments, the vascular intervention device may be fully deployed, in which all of the segments have been pushed outside the distal opening 150 of the catheter 144. FIG. 14C shows the vascular intervention device in a re-collapsed state. As shown in FIG. 14C, the vascular intervention device 50 has moved proximally (relative to FIG. 14B) back into the catheter 144 through the distal opening 150 after engaging the thrombus 142 in FIG. 14B. The proximal motion of the device 50 effectively retrieved the thrombus 142 into the catheter 144. The proximal movement caused the expanded segment(s) to revert back to a collapsed state. Suction, aspiration, or negative pressure may be provided as thrombus 142 is brought near distal opening 150, to facilitate capture of thrombus 142 within catheter 144. Further, balloon devices, such as balloon catheters, may be provided and utilized to manage flow through the vasculature at the location of thrombus 142. For example, a balloon may be expanded proximal to distal opening 150 to substantially slow or stop flow downstream to the location of thrombus 142. Use of a balloon and aspiration creates a flow path that facilitates capture of thrombus 142 within catheter 144.

In the embodiment shown in FIGS. 15A-15C, the vascular intervention device 50 includes four segments that are at least partially encapsulated by the catheter 144 which has been inserted into a vasculature 146. The segments are coupled to a tether 140 which can be manipulated by a user to causes proximal or distal translational motions of the device 50. As shown in FIG. 15A, the vascular intervention device 50 is in a collapsed state and the catheter 144 is positioned at or near a thrombus 142 which resides within a vasculature 146.

FIG. 15B shows a vascular intervention device 50 in a deployed or partially-deployed state. As shown in FIG. 15B, the distal and the intermediate segments have been moved distally outside of the distal opening 150 of the catheter 144 and are now in an expanded state. In the embodiment shown in FIG. 15B, the distal segment 56 has been deployed distal to the thrombus 142 while the intermediate segment is positioned to engage the thrombus 142. One of the advantages of multiple segments is that relatively less precision is required during the positioning process since any of the segments can engage the thrombus. Optionally, the relatively distal segments may act as a filter by having, for example, widened portions that increase the occlusiveness of the distal segment. Thus, parts of thrombus that may be broken up during the engagement of the intermediate segment to the thrombus may be filtered downstream by the distal segment. In the embodiment shown in FIG. 15B, a proximal portion of the vascular intervention device 50 is still encapsulated by the catheter 144. In other embodiments, the vascular intervention device 50 may be fully deployed. FIG. 15C shows the vascular intervention device 50 in a re-collapsed state. As shown in FIG. 15C, the vascular intervention device 50 has moved proximally through the distal opening 150 after engaging the thrombus in FIG. 15B. The proximal movement caused the expanded segment(s) to revert back to a collapsed state and effectively retrieved the thrombus 142 into the catheter 144.

Some embodiments provide a device for retrieving vascular debris in a vasculature comprising: at least two segments radially expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; at least one intermediate portion, each intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter comprising the radially largest region of the pivot; a sheath that is configured to encase the segments in the compressed state; and a tether that is configured to retract the expanded segment into the outer sheath.

In some embodiments, the struts are radially-expandable. In some embodiments, at least one strut diverges from the longitudinal axis, divides into at least two struts, merges with a circumferentially adjacent strut, and converges toward the longitudinal axis.

Some embodiments provide a device comprising at least three segments. Some embodiments provide a device comprising at least four segments. Some embodiments provide a device comprising at least five segments. Some embodiments provide a device comprising at least six segments. Some embodiments provide a device comprising at least seven segments. Some embodiments provide a device comprising at least eight segments. Some embodiments provide a device comprising at least nine segments. Some embodiments provide a device comprising at least ten segments.

Some embodiments provide a device for retrieving vascular debris in a vasculature comprising: at least three segments expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; at least two intermediate portion, each intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter comprising the radially largest region of the pivot; a sheath that is configured to encase the segments in a compressed state; and a tether that is configured to retract the segments into the sheath.

Some embodiments provide a method of retrieving vascular debris from a vasculature comprising: inserting into the vasculature of a patient at least a portion of a sheath comprising a distal opening and encasing at least two or more segments expandable from a collapsed state to an expanded state, each segment having a waist comprising the radially largest region of the segment and two longitudinal ends; releasing at least a portion of a segment outside the distal opening wherein at least a portion of the segment expands to engage the vascular debris; and retrieving the segment and at least a portion of the vascular debris inside the sheath.

In some embodiments, the vascular debris is a thrombus or an embolus. In some embodiments, the sheath encapsulates at least three expandable segments. In some embodiments, the outer diameter of the sheath is no larger than 50% of the diameter of the vasculature.

The foregoing description is provided to enable a person skilled in the art to practice the various configurations described herein. While the subject technology has been particularly described with reference to the various figures and configurations, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the subject technology.

There may be many other ways to implement the subject technology. Various functions and elements described herein may be partitioned differently from those shown without departing from the scope of the subject technology. Various modifications to these configurations will be readily apparent to those skilled in the art, and generic principles defined herein may be applied to other configurations. Thus, many changes and modifications may be made to the subject technology, by one having ordinary skill in the art, without departing from the scope of the subject technology.

Furthermore, to the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim.

A phrase such as “an aspect” does not imply that such aspect is essential to the subject technology or that such aspect applies to all configurations of the subject technology. A disclosure relating to an aspect may apply to all configurations, or one or more configurations. An aspect may provide one or more examples of the disclosure. A phrase such as “an aspect” may refer to one or more aspects and vice versa. A phrase such as “an embodiment” does not imply that such embodiment is essential to the subject technology or that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. An embodiment may provide one or more examples of the disclosure. A phrase such as “an embodiment” may refer to one or more embodiments and vice versa. A phrase such as “a configuration” does not imply that such configuration is essential to the subject technology or that such configuration applies to all configurations of the subject technology. A disclosure relating to a configuration may apply to all configurations, or one or more configurations. A configuration may provide one or more examples of the disclosure. A phrase such as “a configuration” may refer to one or more configurations and vice versa.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description.

While certain aspects and embodiments of the invention have been described, these have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms without departing from the spirit thereof. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 

What is claimed is:
 1. A device for retrieving vascular debris in a vasculature comprising: at least two segments radially expandable from a collapsed state to an expanded state, each of the at least two segments having (a) a waist comprising a radially largest region of the segment and (b) two longitudinal ends; at least one intermediate portion, each of the at least one intermediate portion comprising a pivot that connects adjacent segments, each pivot having a diameter less than a diameter of the waist; a tether attached to a proximalmost of the at least two segments and configured to position the at least two segments; wherein each of the at least two segments comprises at least two struts that extend longitudinally from a proximal end to a distal end of the segment, the at least two struts tapering from the waist radially inward toward a longitudinal axis of the device as the at least two struts approach an adjacent intermediate portion.
 2. The device of claim 1, wherein each of the at least two segments have substantially similar waist dimensions in the expanded state.
 3. The device of claim 1, wherein each of the at least two segments have substantially similar waist dimensions in the collapsed state.
 4. The device of claim 1, wherein each of the at least two segments have the same number of struts.
 5. The device of claim 1, wherein the at least one strut extends from the proximal end and divides into at least two sub-struts at the waist, with each of the two sub-struts connecting to a circumferentially adjacent strut extending from the distal end.
 6. The device of claim 1, wherein the at least two segments comprises at least three segments.
 7. The device of claim 1, wherein the diameter of the waist in the expanded state is at least five times larger than the diameter of the pivot.
 8. The device of claim 1, wherein at least one strut is configured to flex along its length, allowing the at least two segments to pivot multiaxially about their respective intermediate portion.
 9. The device of claim 1, wherein the at least one intermediate portion has a longitudinal length less than a longitudinal length of each of the at least two segments.
 10. A system for retrieving vascular debris in a vasculature comprising: at least three segments expandable from a collapsed state to an expanded state, each of the at least three segments having (a) a waist comprising a radially largest region of the segment and (b) two longitudinal ends; at least two intermediate portions, each of the at least two intermediate portions comprising a pivot that connects adjacent segments, each pivot having a diameter less than a diameter of the waist; a sheath configured to encase the at least three segments in the collapsed state; and a tether attached to a proximalmost of the at least three segments and configured to position the at least three segments relative to the sheath.
 11. The system of claim 10, wherein each of the at least three segments have substantially similar waist dimensions in the expanded state.
 12. The system of claim 10, wherein each of the at least three segments have substantially similar waist dimensions in the collapsed state.
 13. The system of claim 10, wherein each of the at least three segments comprises at least two struts that extend from a proximal end to a distal end of the segment.
 14. The system of claim 13, wherein each of the at least two struts tapers from the waist toward a longitudinal axis as it approaches an adjacent intermediate portion.
 15. The system of claim 13, wherein each of the at least two struts extends from a proximal end of the segment and divides into at least two sub-struts at the waist, with each of the two sub-struts connecting to a circumferentially adjacent strut extending from the distal end of the segment.
 16. The system of claim 10, wherein the at least three segments comprises at least four segments.
 17. A method of retrieving vascular debris from a vasculature comprising: inserting into the vasculature of a patient at least a portion of a sheath comprising a distal opening and encasing at least two segments expandable from a collapsed state to an expanded state, each of the at least two segments having a waist comprising a radially largest region of the segment, two longitudinal ends, and at least one intermediate portion comprising a pivot connecting the segment to an axially adjacent segment; expanding at least a portion of the at least two segments into vascular debris; and retrieving the at least two segments and the vascular debris to within the sheath.
 18. The method of claim 17, wherein the vascular debris is engaged with a proximalmost segment of the at least two segments.
 19. The method of claim 17, further comprising: capturing, within a distal segment, vascular debris dislodged from a proximal segment.
 20. The method of claim 17, wherein the at least a portion of the at least two segments becomes engaged throughout the vascular debris.
 21. The method of claim 17, wherein each of the at least two segments expands to substantially similar outer diameters.
 22. The method of claim 17, wherein each of the at least two segments comprises at least two struts that extend from a proximal end to a distal end of the segment.
 23. The method of claim 22, wherein expanding at least a portion of the at least two segments is performed by retracting the sheath relative to the at least two segments.
 24. The method of claim 22, wherein at least one strut diverges from the longitudinal axis, divides into at least two sub-struts that each merge with a circumferentially adjacent strut, and converges toward the longitudinal axis.
 25. The method of claim 22, wherein at least one strut is configured to flex along its length, allowing the at least two segments to pivot multiaxially about their respective intermediate portion
 26. The method of claim 17, wherein the sheath encases at least three expandable segments. 